How to Convert Material Displacement to a Mesh?
What you can do is using a Displace modifier instead of a Displacement node.
To get the same result as your current 3D reliefs, you need to save the black and white image texture you're using in your Displacement node.
Either this image is already existing as one unique image and in that case it will be easy to load it into your Displace modifier, or it's made of a mix of several nodes, in that case I guess you'll need to bake the b&amp;w texture.
To do so, make sure you're in Cycles Render, plug your nodes so that the b&amp;w composition is displayed as a diffuse image on the surface of your plane. Create a new Image Texture in your Shader Editor, don't plug it into anything, inside this Image Texture click New to create a new black image, call it Displace Image for example, keep this node selected.
In the Render panel &gt; Bake, choose Bake Type &gt; Diffuse, disable Direct and Indirect, enable Color, click on Bake, the image called Displaced Image should now be the b&amp;w displacement image.
Once you get your b&amp;w image, use it in the Displace modifier: Create a Displace modifier, click on Texture &gt; New, in the Properties panel &gt; Texture, in the dropdown menu, select Displaced Image.
With the same b&amp;w image, you'll have the same effect, on the left Displacement node, on the right Displace modifier: